Synthesis of zeolitic imidazolate framework-8 modified graphene oxide composite and its application for lead removal.

Abstract

BACKGROUND: The removal of lead ions (Pb2+) from industrial wastewater can be achieved using adsorption technology. Composites of zeolitic imidazolate framework-8 (ZIF-8) and graphene oxide (GO) were prepared via room temperature synthesis (RTS) using RO water as the solvent and by mixing GO with separated parts of ZIF-8 precursors before its combination. Three weight percentages of GO, 10wt%, 30wt% and 50wt%, were used to synthesize ZGH10, ZGH30 and ZGH50 to determine optimum preparation and application conditions. Results: ZGH30 showed the most outstanding performance as an adsorbent for Pb2+ removal from aqueous solution. As captured by field emission scanning electron microscopy image, ZGH30 showed an adequate amount of ZIF-8 grown on all surfaces of thr GO sheet, with an appropriate exposure of GO sheet layers for further Pb2+ interaction. The Pb2+ adsorption test revealed that ZGH30 obtained the optimum operating values between pH 5 and 6, using 10 mg dosage and it could remove ≤97% of 100 mg L−1 Pb2+. Additionally, ZGH30 achieved the most rapid equilibrium time within 10 min, similar to ZGH50, as compared to their individual components, ZIF-8 (240 min) and GO (300 min). The mechanism of Pb2+ adsorption fitted well with a Langmuir isotherm and pseudo-second-order kinetic model. The theoretical maximum adsorption capacities obtained through Langmuir isotherm were 200, 454.55, 476.19, 555.56 and 454.55 mg g−1, for GO, ZH, ZGH10, ZGH30 and ZGH50, respectively. Conclusions: Therefore, ZGH30 hybrid successfully unleashed its potential as the adsorbent for wastewater treatment technology with improved performance after modification.